Test and measurement instruments (e.g. signal capture and analysis instruments such as spectrum analyzers, oscilloscopes, multimeters, network analyzers; signal source instruments such as signal generators, DC sources, and other waveform or power sources) are used to acquire and display measurement data, typically from a device under test (DUT).
Frequently, a user needs to manipulate data gathered by the measurement instrument. For example, the user may want to add two signals together, subtract one signal from another, scale a measurement by a constant factor, etc.
To illustrate further, suppose the measurement instrument is a network analyzer. A network analyzer is capable of measuring the S-parameters of an electrical network. In a two-port network, the S-parameters are denoted by the notation S11, S12, S21, and S22. A user may want compute an equation using two S-parameters for operands as follows:2*(S11)3+S12  equation (1)
Typically, the user would also want to see the result of the equation displayed real-time as it is computed, since the S-parameters may also change with time.
Previously, the user had to explicitly set up a trace identifying the specific data to be measured, prior to or separately from entering the equation. In our network analyzer example, the user would have had to first set up two traces: a first trace (call it “Tr1”) to measure S11, and a second trace (call it “Tr2”) to measure S12. The traces are necessary to indicate to the measurement instrument that further calculations or manipulations of the measured data would be required. After setting up the traces, the user would use the traces to compute an equation containing references to measurement data. For example, equation (1) would have to be entered on a previous measurement instrument as follows:2*pow(Tr1,3)+Tr2.  equation (2)where pow is a “power” function such that pow(X,Y) computes X to the power of Y.
This additional step of setting up traces requires extra work, and makes the process of getting the desired result (the result of computing the equation) more cumbersome for the user.
There remains a need for a simpler way to use measurement data as operands in an equation on a measurement instrument.